Treatment of olefins with liquid anhydrous hydrogen bromide



Patented Aug. 7, 1951 TREATMENT OF OLEFINS WITH LIQUID ANHYDROUS HYDROGEN BROMIDE Carl B. Linn, Riverside, and Robert J. Newman, Lyons, Ill., assignors to Universal Oil Products Company, Chicago, Ill., a corporation oi Delaware No Drawing. Application July 30, 1945,

- Serial No. 607,906

12 Claims.

Thi invention relates to the treatment of olefinic hydrocarbons with anhydrous liquid hydrogen bromide. More particularly, it relates to the production of alkyl bromides from aliphatic olefins. It is also concerned with the manufacture of alkyl aromatic hydrocarbons by the interaction of an aromatic hydrocarbon and an olefin in the presence of hydrogen bromide.

All-:yl bromides have assumed considerable importance in recent years as starting materials for the production of a great many types of organic derivatives. Consequently, the need has arisen for an inexpensive method of preparing these compounds that can be adapted readily to large scale commercial operation. The present invention comprises in part a simple process for manufacturing alkyl bromides which can be easily adapted to commercial practice and which is characterized by high yields of the desired products and low yields of undesired products. This process involves the hydrobromination of olefins with liquid hydrogen bromide in the absence of solvents.

The large demand for alkyl aromatics, such as ethyl benzene, cumene, cymene, etc. is well known. It is another feature of our invention to provide a new method of producing these valuable alkyl aromatics.

In one embodiment our invention consists of a process for producing valuable derivatives of oletinic hydrocarbons which comprises treating said olefins with anhydrous liquid hydrogen bromide. In a more specific embodiment the present invention relates to a process for producing valuable derivatives of olefinic hydrocarbons which comprises treating said olefins with anhydrous liquid hydrogen bromide in the presence of an aromatic hydrocarbon.

Olefins which may be treated in accordance with the present invention may be either normally gaseous or normally liquid and comprise ethylene, propylene, butylenes, amylenes, hexylenes and their higher homologues, including various polymers of normally gaseous olefins. These olefins may be obtained from any source and include products of catalytic and thermal cracking of oils and those obtained by dehydrogenating the corresponding paraffinic hydrocarbons or by dehydrating alcohols.

Aromatic hydrocarbons such as benzene, toluene, other alkylated benzenes, naphthalene, alkylated naphthalenes, other poly-nuclear aromatics, etc, which are alkylated by olefinic hydrocarbons as hereinafter set forth may be obtained by the fractional distillation of petroleum, by the destructive distillation of coal, by the dehydrogenation and cyclization of aliphatic hydrocarbons and of alkylated aromatic hydrocarbons, and by other means.

The present process may be carried out in batch or continuous type operation. In the batch operation of this process anhydrous liquid hydrogen bromide is agitated within a mixer and the olefin is gradually introduced below the surface of the acid. After the olefin has been contacted with the hydrogen bromide for suitable length of time, the agitation may be stopped and the hydrocarbons separated and fractionated to recover the desired products. In the continuous type of operation, the hydrocarbon charge stock is fed to contactors in which intimate contact between the hydrocarbon and acid is maintained. The efliuent from the contactors is treated for the separation of the acid from the hydrocarbon, the acid being returned to the contactors and. the hydrocarbon being fed to the fractionation system. The hydrocarbon stream leaving the separator contains a small amount of dissolved hydrogen bromide, which may be removed by treatment with caustic, by fractionation, or by other suitable means. Hydrocarbons of high molecular weight and low hydrogen content graduall accumulate in the catalyst and should be removed by distillation or other suitable means in order to maintain the activity of the acid at the desired level.

The exact temperatures and pressures which should be employed will depend upon the activity and physical characteristics of the hydrocarbons involved. As a rule, excessive elevated temperatures are not necessary and good results are obtained below 200 C. Only suflicient pressure need be used to maintain the reactants in the liquid phase. Contact times of from about 1 to about 60 minutes are preferable.

The following examples are given to illustrate the character of the results obtained by the use of the present process, although the examples given are not introduced with the intention of unduly restricting the generally broad scope of the invention.

In Examples 1 and 2, the reactions were carried out in a steel turbomixer by charging a liquid hydrogen bromide was first added to the autoclave and then the hydrocarbon was added. Following the period of contacting, the contents were removed and the hydrocarbon product was caustic washed, dried, and analyzed. The op- 6 erating conditions and results of these runs are summarized in the following table.

Example No 1 2 3 4 I 10 Turbomixer Rotating Apparatus u Autoclave 0 Temperature, "C 1 15 Time, H0l11 l'S 3.0 4. 8 4 fm t l 165 150 360 400 15 Final 100 10 200 375 i'i gr 227 191 147 137 Isobutane 295 0 0 0 Normal Butan 90 0 0 0 Benzellie 3 4g 8g 33 2o Propy ene R Ethylerae... 0 0 22 26 eoovery, ram

Isobutane 300 Sec. But lBromide Higher B biling Point Material. Benzene Isopropyl Bromide Cumene Higher Boiling Point MateriaL.

Benzene .0 .8 Unreacted Ethylene 7.0 2.0 Ethyl Bromide. 35. 2 39. 4 Ethylbenzene... 8. 8 l8. 8 Diethylbenzene 2. 3 10. 5 Higher Boiling Point Material. 6. 5 30 1 Maximum.

In Example 1, 86 mol percent of the butene charged was actually recovered as secondary butyl bromide in spite of inevitable losses. The higher boiling material contained bound bromide. It will be noted that this experiment was carried out in the presence of isobutane, which acted as a diluent. In Example 2, 74% of the propylene was converted to isopropyl bromide and 3.6% of the propylene charged was recovered as cumene. At room temperature, as shown in Example 3, 32% of the ethylene charged did not react. Of that which did react, 60% went to ethyl bromide and 16% to ethylbenzene. The experiment was repeated by adding the reactants and catalyst to the autoclave at room temperature and heating to 150 C. in Example 4. Under these conditions only 8% of the ethylene did not react. Of that which did react, 42% went to ethyl bromide, 21% to ethylbenzene, and 18% to diethylbenzene.

The results of these experiments show that oleflns can be converted into alkyl bromides in excellent yields by treatment of said oleflns with 5 liquid hydrogen bromide. This is true for pure oleflns as well as for mixtures of oleflns with other hydrocarbons. The results also show that aromatic hydrocarbons can be alkylated with olefins in the presence of liquid hydrogen bromide.

In one modification of our invention, mixtures of olefins and other hydrocarbons, particularly mixtures of oleflns and parafllns, can be separated readily without the side reactions which characterize mose chemical methods of separation. As illustrated in Example 1, a narrow boiling mixture of paraflins and oleflns are contacted with liquid hydrogen bromide and the oleflns are thereby converted to alkyl bromides. The hydrocarbons are separated from the acid and the bromides are recovered by fractionation or other suitable means.

' We claim as our invention: 1. A process for producing valuable derivativ s oi olefinic hydrocarbons which comprises treating said olefins with a halide material consisting essentially of anhydrous liquid hydrogen bromide.

2. A process for producing alkyl bromides which comprises reacting an olefin with anhydrous liquid hydrogen bromide.

3. A process for producing alkyl bromides which comprises reacting a normally gaseous olefin with anhydrous liquid hydrogen bromide.

4. A process for producing alkyl bromides which comprises reacting a normally liquid olefin with anhydrous liquid hydrogen bromide.

5. A process tor the manufacture of ethyl bromide which comprises reacting ethylene with anhydrous liquid hydrogen bromide.

6. A process for the manufacture of propyl bromide which comprises reacting propylene with anhydrous liquid hydrogen bromide.

'7. A process for the manufacture of butyl bromide which comprises reacting butylene with anhydrous liquid hydrogen bromide.

8. A process for producing alkylated aromatic hydrocarbons which comprises contacting an arcmatic hydrocarbon with an oleflnic hydrocarbon under alkylating conditions in the presence of a halide catalyst consisting essentially of anhydrous liquid hydrogen bromide.

9. A process for producing ethylated benzene which comprises subjecting benzene to contact with ethylene under alkylating conditions in the presence of a halide catalyst consisting essentially of anhydrous liquid hydrogen bromide.

10. A process for producing propylated benzene which comprises subjecting benzene to contact with propylene under alkylating conditions in the presence of a halide catalyst consisting essentially of anhydrous liquid hydrogen bromide.

11. A process for the separation of oleflns from hydrocarbon mixtures containing oleflns which comprises treating said mixtures with anhydrous liquid hydrogen bromide, separating the hydrocarbon product from the acid layer, and recovering the alkyl bromides from said hydrocarbon product.

12. A process for producing an alkyl bromide and an alkylated aromatic hydrocarbon which comprises subjecting a mixture of an olefin, an aromatic hydrocarbon and a halide catalyst consisting essentially of anhydrous hydrogen bromide to reaction at an alkylating temperature and under suflicient pressure to maintain the hydrogen bromide in liquid phase.

CARL B. LINN. ROBERT J. NEWMAN.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,058,465 Kharash Oct. 27, 1936 2,406,869 Upham Sept. 3, 1946 OTHER REFERENCES Simons et al.: Hydrogen Chloride as a Condensing Agent, J. A. C. 8., vol. 66, pages 1309-12 (August 1944) (4 pages).

International Critical Tables, vol. 3, page 228.

Kirschbaum: Distillation and Rectification, pages 8 to 10 (1948). (German edition published prior to 1943). 

12. A PROCESS FOR PRODUCING AN ALKYL BROMIDE AND AN ALKYLATED AROMATIC HYDROCARBON WHICH COMPRISES SUBJECTING A MIXTURE OF AN OLEFIN, AN AROMATIC HYDROCARBON AND A HALIDE CATALYST CONSISTING ESSENTIALLY OF ANHYDROUS HYDROGEN BROMIDE TO REACTION AT AN ALKYLATING TEMPERATURE AND UNDER SUFFICIENT PRESSURE TO MAINTAIN THE HYDROGEN BROMIDE IN LIQUID PHASE. 